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Date: Tue, 4 Oct 2011 04:38:59 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Frederic Weisbecker <fweisbec@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Paul Menage <paul@...lmenage.org>,
Li Zefan <lizf@...fujitsu.com>,
Johannes Weiner <hannes@...xchg.org>,
Aditya Kali <adityakali@...gle.com>,
Oleg Nesterov <oleg@...hat.com>,
Kay Sievers <kay.sievers@...y.org>,
Tim Hockin <thockin@...kin.org>, Tejun Heo <tj@...nel.org>,
Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH 09/10] cgroups: Allow subsystems to cancel a fork
On Mon, Oct 03, 2011 at 09:07:11PM +0200, Frederic Weisbecker wrote:
> Let the subsystem's fork callback return an error value so
> that they can cancel a fork. This is going to be used by
> the task counter subsystem to implement the limit.
>
> Suggested-by: Oleg Nesterov <oleg@...hat.com>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Acked-by: Kirill A. Shutemov <kirill@...temov.name>
> Cc: Paul Menage <paul@...lmenage.org>
> Cc: Li Zefan <lizf@...fujitsu.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Aditya Kali <adityakali@...gle.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Kay Sievers <kay.sievers@...y.org>
> Cc: Tim Hockin <thockin@...kin.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Kirill A. Shutemov <kirill@...temov.name>
> Cc: Containers <containers@...ts.linux-foundation.org>
> ---
> include/linux/cgroup.h | 20 ++++++++++++++------
> kernel/cgroup.c | 23 +++++++++++++++++++----
> kernel/cgroup_freezer.c | 6 ++++--
> kernel/exit.c | 2 +-
> kernel/fork.c | 7 +++++--
> 5 files changed, 43 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index b62cf5e..9c8151e 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -17,10 +17,11 @@
> #include <linux/rwsem.h>
> #include <linux/idr.h>
>
> +struct cgroup_subsys;
> +
> #ifdef CONFIG_CGROUPS
>
> struct cgroupfs_root;
> -struct cgroup_subsys;
> struct inode;
> struct cgroup;
> struct css_id;
> @@ -32,9 +33,11 @@ extern int cgroup_lock_is_held(void);
> extern bool cgroup_lock_live_group(struct cgroup *cgrp);
> extern void cgroup_unlock(void);
> extern void cgroup_fork(struct task_struct *p);
> -extern void cgroup_fork_callbacks(struct task_struct *p);
> +extern int cgroup_fork_callbacks(struct task_struct *p,
> + struct cgroup_subsys **failed_ss);
> extern void cgroup_post_fork(struct task_struct *p);
> -extern void cgroup_exit(struct task_struct *p, int run_callbacks);
> +extern void cgroup_exit(struct task_struct *p, int run_callbacks,
> + struct cgroup_subsys *failed_ss);
> extern int cgroupstats_build(struct cgroupstats *stats,
> struct dentry *dentry);
> extern int cgroup_load_subsys(struct cgroup_subsys *ss);
> @@ -479,7 +482,7 @@ struct cgroup_subsys {
> struct task_struct *tsk);
> void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
> struct cgroup *old_cgrp, struct task_struct *tsk);
> - void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
> + int (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
> void (*exit)(struct cgroup_subsys *ss, struct cgroup *cgrp,
> struct cgroup *old_cgrp, struct task_struct *task);
> int (*populate)(struct cgroup_subsys *ss,
> @@ -636,9 +639,14 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
> static inline int cgroup_init_early(void) { return 0; }
> static inline int cgroup_init(void) { return 0; }
> static inline void cgroup_fork(struct task_struct *p) {}
> -static inline void cgroup_fork_callbacks(struct task_struct *p) {}
> +static inline int cgroup_fork_callbacks(struct task_struct *p,
> + struct cgroup_subsys **failed_ss)
> +{
> + return 0;
> +}
> static inline void cgroup_post_fork(struct task_struct *p) {}
> -static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
> +static inline void cgroup_exit(struct task_struct *p, int callbacks,
> + struct cgroup_subsys *failed_ss) {}
>
> static inline void cgroup_lock(void) {}
> static inline void cgroup_unlock(void) {}
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 709baef..018df9d 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -4540,8 +4540,11 @@ void cgroup_fork(struct task_struct *child)
> * tasklist. No need to take any locks since no-one can
> * be operating on this task.
> */
> -void cgroup_fork_callbacks(struct task_struct *child)
> +int cgroup_fork_callbacks(struct task_struct *child,
> + struct cgroup_subsys **failed_ss)
> {
> + int err;
> +
> if (need_forkexit_callback) {
> int i;
> /*
> @@ -4551,10 +4554,17 @@ void cgroup_fork_callbacks(struct task_struct *child)
> */
> for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
> struct cgroup_subsys *ss = subsys[i];
> - if (ss->fork)
> - ss->fork(ss, child);
> + if (ss->fork) {
> + err = ss->fork(ss, child);
> + if (err) {
> + *failed_ss = ss;
> + return err;
> + }
> + }
> }
> }
> +
> + return 0;
> }
>
> /**
> @@ -4612,7 +4622,8 @@ void cgroup_post_fork(struct task_struct *child)
> * which wards off any cgroup_attach_task() attempts, or task is a failed
> * fork, never visible to cgroup_attach_task.
> */
> -void cgroup_exit(struct task_struct *tsk, int run_callbacks)
> +void cgroup_exit(struct task_struct *tsk, int run_callbacks,
> + struct cgroup_subsys *failed_ss)
> {
> struct css_set *cg;
> int i;
> @@ -4641,6 +4652,10 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
> */
> for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
> struct cgroup_subsys *ss = subsys[i];
> +
> + if (ss == failed_ss)
> + break;
> +
> if (ss->exit) {
> struct cgroup *old_cgrp =
> rcu_dereference_raw(cg->subsys[i])->cgroup;
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index c1421a1..30a4332 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -187,7 +187,7 @@ static int freezer_can_attach_task(struct cgroup *cgrp, struct cgroup *old_cgrp,
> return 0;
> }
>
> -static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
> +static int freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
> {
> struct freezer *freezer;
>
> @@ -207,7 +207,7 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
> * following check.
> */
> if (!freezer->css.cgroup->parent)
> - return;
> + return 0;
>
> spin_lock_irq(&freezer->lock);
> BUG_ON(freezer->state == CGROUP_FROZEN);
> @@ -216,6 +216,8 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
> if (freezer->state == CGROUP_FREEZING)
> freeze_task(task, true);
> spin_unlock_irq(&freezer->lock);
> +
> + return 0;
> }
>
> /*
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 2913b35..abab32b 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -994,7 +994,7 @@ NORET_TYPE void do_exit(long code)
> */
> perf_event_exit_task(tsk);
>
> - cgroup_exit(tsk, 1);
> + cgroup_exit(tsk, 1, NULL);
>
> if (group_dead)
> disassociate_ctty(1);
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 8e6b6f4..ee8abdb 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1058,6 +1058,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
> int retval;
> struct task_struct *p;
> int cgroup_callbacks_done = 0;
> + struct cgroup_subsys *cgroup_failed_ss = NULL;
>
> if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
> return ERR_PTR(-EINVAL);
> @@ -1312,8 +1313,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
> /* Now that the task is set up, run cgroup callbacks if
> * necessary. We need to run them before the task is visible
> * on the tasklist. */
> - cgroup_fork_callbacks(p);
> + retval = cgroup_fork_callbacks(p, &cgroup_failed_ss);
> cgroup_callbacks_done = 1;
> + if (retval)
> + goto bad_fork_free_pid;
>
> /* Need tasklist lock for parent etc handling! */
> write_lock_irq(&tasklist_lock);
> @@ -1419,7 +1422,7 @@ bad_fork_cleanup_cgroup:
> #endif
> if (clone_flags & CLONE_THREAD)
> threadgroup_fork_read_unlock(current);
> - cgroup_exit(p, cgroup_callbacks_done);
> + cgroup_exit(p, cgroup_callbacks_done, cgroup_failed_ss);
> delayacct_tsk_free(p);
> module_put(task_thread_info(p)->exec_domain->module);
> bad_fork_cleanup_count:
> --
> 1.7.5.4
>
--
Kirill A. Shutemov
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